The present invention is generally directed to an information retrieval system of the type which automatically retrieves selected information bearing elements for inspection. The present invention is more particularly directed to the control and marker sensing system for an automatic film searching and retrieval system for use with film having a plurality of consecutively numbered frames, and wherein each frame includes an information image and an adjacent frame marker.
Information retrieval systems are well known. One efficient type of retrieval system that has found widespread acceptance is often referred to as a microfilm retrieval system. In such systems, copies of documents and/or data are recorded on film such as 16 mm. film wherein each film frame comprises an information bearing element. With the size of the film frame being on the order of 1 mm. per document inch, such size reduction affords a substantial savings in information storage volume and greatly simplifies handling of the information. Such a reduction in size necesarily precludes direct reading of the information bearing elements. The usual procedure for reading them is to project the film frame images onto a screen and to magnify them to a size corresponding approximately to the original size of the information document that is recorded.
Because literally thousands of information bearing elements or film frames comprise a roll of microfilm, searching for a particular image film frame can be time consuming. As an example, microfilm reels are known to include information bearing elements or frames on the order of 40,000 frames per reel. To provide ready access to a preselected information bearing element or film frame, automatic search techniques have been developed in the form of automatic retrieval systems.
In such systems, the film frames of the microfiln reels are numbered consecutively for identification and each film frame has an adjacent marker which may be counted and the identification numbers displayed. Hence, during the search cycle, the counter provides the current number of film frames currently being sensed and at the end of a scan cycle, provides the current number of the film frame being inspected.
Retrieval systems also include a means for entering a target number which identifies the film frame to be inspected. Suitable logic control within the retrieval systems determine from the current number and the target number whether the film is to be driven in an up direction or a down direction to arrive at the preselected film frame to be inspected.
Retrieval systems of the prior art have been generally successful in locating preselected information bearing elements or film frames for inspection where the microfilm includes only one set of film frames which are consecutively numbered for identification and wherein each film frame is associated with an identifiable marker. However, additional microfilm formats have been developed to greatly increase the number of information bearing elements or film frames which may be contained upon a microfilm reel and formates wherein the film frames are divided into groups or batches wherein the first film frame of each group is associated with a group identification marker and wherein the film frames comprising each group are consecutively numbered for identification within each group.
In the format wherein an increased number of film frames are contained upon a microfilm reel, first and second sets of information bearing elements or film frames are provided. The first set of film frames are generally located at the top half of the film and each film frame of the first set is numbered consecutively for identification in increasing order as the film is driven in a first direction. A second set of film frames is provided in the bottom half of the microfilm and the film frames comprising the second set are consecutively numbered but in increasing order when the film is driven in a second direction which is opposite from the first direction. Each film frame of the first set is associated with an identifiable marker comprising a first set of markers at the top edge of the microfilm and each film frame comprising the second set of film frames is associated with an identifiable marker at the bottom edge of the microfilm and comprise a second set of identifiable markers. Since the first set of markers are at the top edge of the microfilm and the second set of the markers are at the bottom edge of the microfilm, the first and second sets of the markers are spaced apart. This format is generally referred to as the "Duo-Duplex" format.
When the film frames are divided into groups or batches, each group or batch includes a plurality of image film frames. The first film frame of each group or batch is associated with an identifiable group marker which is located at the bottom edge of the film. Each film frame of each group is associated with an identifiable marker which is at the top edge of the film. The groups are consecutively numbered as are the film frames in each group. Thus, the group identifiable markers may be considered a second set of markers and the markers associated with each film frame may be considered a first set of markers. With the first set of markers being at the top edge of the film and with the second set being at the bottom edge of the film, the first and second sets of markers are also spaced apart.
It is, therefore, a general object of the present invention to provide a new and improved control and marker sensing system for an automatic film searching and retrieval system which adapts the system for locating a preselected film frame wherein the film frames are arranged in the standard format including a single set of film frames associated with identifiable markers, in the Duo-Duplex format having first and second sets of film frames and first and second sets of identifiable markers, and in the batch format wherein the film frames are divided into a plurality of batches.
It is a more particular object of the present invention to provide a control and marker sensing system for an automatic film searching and retrieval system which includes a marker sensor for sensing first and second sets of identifiable markers, a detector for detecting which set of markers is being sensed, and interface means for selectively coupling the marker sensor to the system counter responsive to the detector to thereby cause the counter to maintain the accurate location of the film frames regardless of the direction in which the film frames are being driven.
It is a still more particular object of the present invention to provide a control system for an automatic film searching and retrieval system which adapts the system for locating a preselected group of film frames and a preselected film frame within the preselected film frame group.